Well I guess the first step should be to see how the higher frequencies, say 70 hz and up register on the subwoofers first before I pick a point for the mids to kick in?

Or would the range from 250 down to the lpf be negligable because of the rolloff of the two filters?

 

You rarely want subwoofers to run higher than 60-80hz. It is almost always nasty.

What diameter are the mids? If a 5.25 or 6.5, a 200uF cap would be all you likely need on them if you're trying to keep it simple.